The present invention is directed to a portable, internal combustion power operated working device, such as a tool for driving fastening elements into a receiving material. The working device includes a housing containing a combustion chamber with a piston guided within a guide chamber with the guide chamber displaceably mounted in the combustion chamber. The piston can be driven axially within the guide chamber by gas pressure generated by combustion of an air-fuel mixture within the combustion chamber. Means are provided for preparing the air-fuel mixture to be supplied to the combustion chamber.
Such a working device is known from the U.S. Pat. No. 4,759,318.
The known working device includes a combustion chamber for burning an air-fuel mixture, and a piston guided in a guide cylinder and driven by the gas pressure generated by the combustion of an air-fuel mixture. In addition, there is an arrangement for preparing the air-fuel mixture.
If this known working device is to be operated, first air must be pumped into the combustion chamber by a separate pumping apparatus located in the handle of the device and operated manually for forming the air-fuel mixture along with the injected fuel. Particularly in a large volume device, an adequate turbulence of the air-fuel mixture is not assured, and, in addition, considerable output fluctuations develop, due to the injection of liquid gas, independent of the ambient pressure, into the combustion chamber.